The most common and most likely answer to this crossword clue is the 14 letter word TUMBLER-SWITCH
T
U
M
B
L
E
R
-
S
W
I
T
C
H
Buddy explains!
The straight part
We know that "Current controller" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case current controller = tumbler-switch.The cryptic/wordplay part
In cryptic crossword there's often an wordplay/cryptic part as well.This part involves a more complex hint, such as an anagram, homophone, hidden word, etc.
Sadly, We don't have an explanation for this specific crossword clue yet.